It turns north because of the Coriolis Effect. Everything in the northern hemisphere deflects to the right. Plus the prevaling soutwesterlies give it an added push.
Except in Shep Smith's bathtub. Then, all bets are off.
http://www.freerepublic.com/focus/f-news/1474026/posts?page=35#35
Shep Smith: "The water level in New Orleans keeps rising, and nobody knows why."
Alberta's Child: "What is he, a freakin' moron? The water level keeps rising because the elevation of New Orleans is lower than the elevation of the adjacent waterways. Maybe Shep ought to go home and try to fill the north half of his bathtub to get an understanding of some very rudimentary principles of fluid mechanics."